1. Field of the Invention
The present invention relates to an organic electroluminescence display and, more particularly, to an active matrix organic electroluminescence display in which two opposite pixels are formed in one pixel portion to achieve a high aperture ratio and to facilitate a fabrication process.
2. Description of the Related Art
A cathode ray tube (CRT) as one of normally used display devices is primarily used for televisions (TVs) as well as monitors of measurement instruments, information terminals, and the like. However, the cathode ray tube cannot satisfy a need for compact and lightweight electronic products because of its weight and size.
Flat panel display devices having compact and lightweight features have been attracted attention as substitutes for the CRT. The flat panel display devices include a liquid crystal display (LCD), an organic electro luminescence display (OELD), and the like.
Of these flat panel display devices, the organic electroluminescence display is an electro luminescence display that emits light when excitons are transitioned from an excited state to a ground state. The excitons are created when respective electrons and holes from an electron injection electrode (i.e., a cathode) and a hole injection electrode (i.e., an anode) are injected into an emission layer and the injected electrons and holes are combined.
This principle eliminates a need for a separate light source, which is needed for a conventional thin film liquid crystal display device. It is, therefore, possible to reduce the volume and weight of the device.
The organic electroluminescence display may be classified into a passive matrix manner and an active matrix manner according to a driving manner.
The passive matrix organic electroluminescence display may be easily fabricated because of its simple configuration. However, there are disadvantages of high power consumption and a difficulty in making a large-sized display device. Also, in making the passive matrix organic electroluminescence display, the aperture ratio is reduced as the number of lines are increased.
For these reasons, the passive matrix organic electroluminescence display is used for a small-sized display device while the active matrix organic electroluminescence display is used for a large-sized display device.
The conventional organic electroluminescence display has a problem in that the thickness of the organic emission layer is not uniform in a stepped portion of the opening corresponding to each pixel, which makes it impossible to achieve uniform luminescence properties.
A method of forming an opening in a stripe manner to solve the aforementioned problem was introduced, as disclosed in Korean Laid-open Patent No. 2002-0077241. A method of forming an opening in a delta manner was also introduced.
There is, however, a problem that when the stripe or delta type is used to increase an aperture ratio, visibility of the organic electroluminescence display is degraded due to optical interference between adjacent pixels.
Further, in the case of forming the opening in the dot manner, the stripe type and the delta type in the organic electroluminescence display, R, G, B pixels are arranged to have the same form in uniform positions. That is, the pixels are arranged uniformly. Since the minuteness of a pattern is inversely proportional to a high aperture ratio, there is a problem associated with the manner of increasing the aperture ratio of the pixel in a stripe or delta type for a high quality data processing that requires a minute pattern as well as a high aperture ratio.